Wastewater is a by-product of residential, commercial, agricultural, or industrial waste production such as that from homes, farms, and manufacturing plants, among others. Every day there are an estimated 40 billion gallons of wastewater created in POTWs (Publically Owned Treatment Works) alone (Center for Sustainable Systems, University of Michigan, 2010). The accumulation of debris in WWTPs (Wastewater Treatment Plants) and other wastewater processing equipment (such as drainlines, septic systems, sewers, grease traps, lift-stations, holding tanks and ponds) presents a major problem not only to the limitation of water re-use but also as a major cause of costly equipment failure throughout the processing of the wastewater. FOG (Fats, Oils, and Grease) refers to a general collection of lipids which are typically found in wastewater and make up a significant portion of problematic wastewater debris. Partially due to its insolubility and density contrasting the aqueous phase, FOG floats on top of the wastewater and accumulates throughout the pipes and holding areas of wastewater treatment process. It is for this reason that there have been major efforts focused on the removal of FOG from wastewater early in the processing, prior to its movement downstream.
Grease, vegetable oil and the like are potentially valuable waste products generated by restaurants, other food preparation establishments, and industrial and/or commercial facilities in which animal and/or vegetable material is processed. However, these lipid-containing waste materials are generally contaminated with high levels of undesirable fatty acids. If these free fatty acids could be economically and efficiently eliminated, while retaining substantially all of the fats in an unaltered state, the fats could be reclaimed for further processing into desirable fuels and/or used in a variety of products.
A problem with reclamation of triglycerides from fatty wastes (i.e., fat-containing waste material from food processing or other industries) is that the fatty waste material typically contains undesirably large amounts of free fatty acids (i.e., fatty acids that are not bonded to another chemical moiety by an ester linkage). Free fatty acids are undesirable for a variety of reasons. The presence of a substantial amount of free fatty acids in reclaimed triglycerides imparts an offensive odor and/or an undesirably yellow or brown color that renders the compositions unsuitable for many applications. Further, reclaimed triglycerides that contain large amounts of free fatty acids cannot be converted to biodiesel fuel using convention techniques employing an alkaline catalyst, and alternative methods involving acid catalysts are too slow to provide practical and economical production of biodiesel fuel.
In many, perhaps most, municipalities, restaurants and other establishments generating a significant quantity of fat-containing lipid waste material are required to intercept or trap such material to prevent it from flowing directly into the sewer. The intercepted or trapped fat-containing waste material is stored in what is commonly referred to as a grease trap. The fat-containing waste material is typically periodically removed from the grease trap for disposal. Bacteria are sometimes added to these systems for intercepting fat-containing waste material in order to decrease the frequency at which material must be removed from the grease trap. The strains typically used for bioaugmentation of materials collected in grease traps produce extra-cellular lipase, which hydrolyzes and breaks the ester bond between the glycerol and fatty acid moieties of triglycerides. The free fatty acids which are produced upon hydrolysis of triglycerides are difficult to degrade, and can cause a pH drop, clogging and malodors, as well as rendering the materials unsuitable for conversion to fuels or other uses.